Interpretive Summary: The Mediterranean fruit fly (medfly) is the most important pest of fruits and vegetables world wide. Because of the threat of this fruit fly, much emphasis has been placed on the development of biorational control measures such as sterile insect technology (SIT) for suppression of this pest. Aromatherapy, in which male mating success is improved by exposing sterile males to odors from plant essential oils, is used to improve effectiveness of flies released for SIT. It was not know if a similar effect would be produced by exposure to tea tree oil (TTO), an essential oil that is a short range attractant for males, Therefore scientists at APHIS, Hilo, HI conducted tests in collaboration with scientists at SHRS to evaluate mating success of males that had been exposed to TTO and to compare long range attraction to traps baited with TTO versus traps baited with trimedlure, the standard male attractant. TTO aroma was found to increase mating success in treated males over non-exposed males. Traps baited with TTO, however, were not as effective as traps baited with trimedlure. Results of this study will be used to further understand the role of non-host plant volatiles in medfly biology and may lead to the development of improved tools for insect control. This information will be used by growers and by regulatory agencies for pest detection and suppression.

Technical Abstract: The aroma of various plant essential oils has been shown to enhance the mating competitiveness of males of the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann). Laboratory observations revealed that male medflies show strong short-range attraction to tea tree oil (TTO hereafter) derived from leaves of the Australian plant Melaleuca alternifolia (Maiden & Betch) Cheel. The present study was undertaken to i) compare the attractiveness of TTO to trimedlure (the male lure routinely used in detection surveys) in field and field cage tests and ii) assess the influence of TTO exposure on male mating success under conditions of varying dose, duration of post-exposure (i.e., pre-test) interval, and access (contact possible or not) to the TTO source. TTO-baited traps captured 50% as many males as trimedlure-baited traps in field cages but only 8% as many males as trimedlure-baited traps in the open field. Males exposed to pure TTO or dilutions of 50% and 5% TTO in hexane had higher mating success than control, non-exposed males in tests conducted 1 d after exposure. TTO-exposed males also had a mating advantage when i) tested 3 d after exposure and ii) physical contact with the TTO source was prevented. In an additional experiment, TTO exposure was found to enhance the mating competitiveness of mass-reared, sterile males in competition against wild males for copulations with wild females in tests conducted 1 or 3 d after exposure.